Centrifugal clutch assembly

ABSTRACT

In a centrifugal clutch including a drive shaft, a pair of pulley flanges mounted on said drive shaft and providing therebetween a groove for a V-belt, one of the pulley flanges being axially movable on the drive shaft to vary the radial position of the V-belt with respect to the pulley flanges, apparatus for axially moving said movable pulley flange in response to the angular velocity of the drive shaft, comprising a cam ramp fixedly mounted to said drive shaft in spaced relationship with the side of the movable pulley flange away from the other pulley flange, said cam ramp including a portion curved toward said movable pulley flange, and a weight mounted for rolling radial movement on said movable pulley flange and on said cam ramp.

United States Patent Schupan [4 1 Aug. 1, 1972 [54] CENTRIFUGAL CLUTCHASSEMBLY 72 I t F d A. s h Y P I Primary Examiner-C. Husar 1 men or re cupan or a Attorney-George W. Price and Barry H. Fishkin [73] Assignee:AMF Incorporated 22 Filed: Aug. 27, 1970 [57] ABSTRACT In a centrifugalclutch including a drive shaft, a pair of [21] Appl' 674l3 pulleyflanges mounted on said drive shaft and providing therebetween a groovefor a V-belt, one of the pul- [52] us. Cl. ..74/230.l7 E y fl ng s ingaxially movable on the drive shaft to 51 Int. Cl ..F16h 55/52 y theradial Position of the l with ap to [58] Field of Search ..74/230.17 Ethe P y flanges, pp r for wally movmg said movable pulley flange inresponse to the angular [56] References Cited velocity of the driveshaft, comprising a cam ramp fixedly mounted to said drive shaft inspaced relationship UNITED STATES PATENTS with the side of the movablepulley flange away from the other pulley flange, said cam ramp includinga g 2 galleher 2 portion curved toward said movable pulley flange, and30l7783 J1962 g fi 'i" E a weight mounted for rolling radialmovement onsaid 3230787 1/1966 z g er rugg E movable pulley flange and on said camramp. 3,574,366 4/1971 Thostenson ..74/230.17 E 4 Claims, 9 DrawingFigures PA'TENTEDAUG 1 I912 SHEET 1 OF 4 INVENTOR.

FRED A. SCHUP N ATTORNEY PATENTEUAUB Y #972 SHEET 2 0F 4 .INVENTOR FREDAZ'. SCHUPAN B Y I ATTORNEY PATENTEDR B 1 I972 sum 3 0r 4 INVENTOR FREDA. SCHUPAN ATTORNEY PATENTED M191 1972 SHEET H 0F 4 IN VENTOR FREDSCHUPAN ATTORNEY BACKGROUND This invention relates to variable speedV-belt transmissions by which power is transmitted from a driving shaftto a driven shaft and more particularly to an improved centrifugalclutch for such variable speed transmissions. Transmissions of this typeare commonly utilizedin small vehicles, such as snowmobiles, golf carts,motorcycles and the like.

In transmissions of this type each of the shafts commonly carries apulley including a pair of opposed pulley flanges which between themprovide a V-shaped groove adapted to receive a belt connecting the twopulleys. The V-belt is normally mounted at the bottom of the pulley onthe driving shaft and the top of the pulley on the driven shaft. Oneflange of each of the pulleys is movable against a bias. The pulley onthe driving shaft is operatively connected to means having centrifugalweights for shifting the movable pulley flange in response to enginespeeds and is called a centrifugal clutch With increasing drive shaftspeed the centrifugal clutch will close the space between the pulleyflanges and urge the V-belt outwardly. This will pull the belt inwardlyin the pulley on the driven shaft thus moving the transmission from ahigh torque to a high speed mode.

In applications where this type of transmission is utilized,particularly snowmobiles, the sensitivity of the drive with respect tothe throttle is of the utmost importance. The operator of the vehicleshould have a sensitive control wherein the speed of the vehicle can besmoothly accelerated and decelerated to provide the needed control ofthe vehicle for the uneven terrain that these vehicles often are drivenacross. In the past such vehicle speed control has been lacking due to apredilection for the centrifugal weights in the clutch to stick and beresponsive only to large increases in engine speed, causing lurching ofthe vehicle when the throttle setting is changed.

SUMMARY It is, therefore, an object of this invention to provide animproved variable speed drive for small vehicles.

It is a further object of this invention to provide a centrifugal clutchfor a variable speed transmission having increased responsiveness toengine speed.

It is a more specific object of this invention to provide an improvedcentrifugal weight assembly for a centrifugal clutch.

In accordance with these and other objects, apparatus according to theinvention may comprise in combination with a drive shaft, a pair ofpulley flanges mounted on said drive shaft and providing therebetween agroove for a V-belt, one of the pulley flanges being axially movable onthe drive shaft to vary the radial position of the V-belt with respectto the pulley flanges, means for axially moving said pulley flanges inresponse to the angular velocity of the drive shaft, including: a camramp fixedly mounted to said drive shaft in spaced relationship with theside of the movable pulley flange away from the other pulley flange,said cam ramp including a portion curved toward said movable pulleyflange, a weight mounted for rolling movement between said cam ramp andsaid movable pulley flange and guide means for maintaining the rollingof said weight in a radial direction.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of a snowmobileincorporating the invention.

FIG. 2 is a partial plan view of the snowmobile shown in FIG. 1.

FIG. 3 is a side elevation view of a centrifugal clutch according to theinvention.

FIG. 4 is a sectional view of a portion of the clutch shown in FIG. 3taken along line 4-4 of FIG. 3.

FIG. 5 is a side elevation view of an alternate embodiment of acentrifugal clutch according to the invention.

FIG. 6 is a sectional view of a portion of the clutch shown in FIG. 5taken along line 6-6 of FIG. 5.

FIG. 7 is a side elevation view of another alternate embodiment of acentrifugal clutch according to the invention.

FIG. 8 is a sectional view of a portion of the clutch taken along line8-8 of FIG. 7.

FIG. 9 is a sectional view of a portion of the clutch taken along 9-9 ofFIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to the drawings,a preferred embodiment of the invention is shown in connection with asnowmobile, but it is to be understood that it could be utilized inother vehicle applications.

In general, a snowmobile 10 includes a frame 12, a seat 14 for theoperator and a steering handle 16 for manipulating a pair of steeringskis 18 through a shaft 19 and a linkage 20. A traction belt 22 ismounted over a suspension 24 which is mounted in turn to the frame 12.The traction belt is driven by a pair of drive sprockets 26 mounted on ashaft 28 and each engageable with a rectilinear succession of sprocketholes 30 in the traction belt. The sprocket drive shaft 28 is driven bya motor 32 through a variable speed drive, generally designated 34.

The variable speed drive 34 includes a drive shaft 36 extending from androtated by motor 32. First and second pulley flanges, 38 and 40respectively, are mounted on drive shaft 36 for rotation along therewithand provide therebetween a groove 42 for engaging and driving a V-belt44. First pulley flange 38 is fixed on shaft 36 against axial movement.The second pulley flange 40 is axially shiftable to vary the size ofgroove 42 and thus the radial position of V-belt 44 with respect to thepulley flanges. A spring 43 is mounted in a recess 43a in the pulleyflange 40 to bias the latter away from pulley flange 38, a clip 43bretaining the spring in place. The pulley flanges 38 and 40 are mountedon shaft 36 so that at engine idling speed there is a gap between theV-belt and the pulley flanges and the V- belt is not driven thereby.

A driven shaft 46 is mounted in parallel spaced relationship with driveshaft 36. A pair of opposed pulley flanges, 48 and 50 respectively, aremounted on the driven shaft 46 and form a groove 52 therebetween inspaced relationship with groove 42 for receiving V-belt 44 such thatshaft 46 can be driven from shaft 36 by the V-belt 44. The sprocketwheel drive shaft 28 is driven from shaft 46 through a sprocket 54mounted thereon, a sprocket (not shown) mounted in spaced relationshiptherewith on the sprocket wheel drive shaft 28 and a chain 56 mountedover both sprockets.

Pulley flange 48 is axially movable on driven shaft 46 against a springbias (not shown) mounted in a housing 58. The normal position of thepulley flanges 48 and I 50, that at engine idling speed, is such thatthe V-belt is at its radially outward position. I

A centrifugal clutch 60 (FIG. 3) is mounted on shaft 36 for axiallyshifting pulley flange 40 in response to variations in the angularvelocity of the drive shaft. The centrifugal clutch includes a cam ramp62.affixed to the shaft, spring means (not shown) between the cam rampand pulley flange 40 to bias the latter away from pulley flange 38 andinto the idle position shown in the bottom half of FIGS. 3 and 5, and aplurality of centrifugal weights 66 mounted for rolling movement betweensaid cam ramp and said movable pulley flange.

Referring now to FIGS. 3 and 4, each of the centrifugal weights 66includes a rod 70, first and second wheels 74 and 76 mounted on said rodand separated by a bearing member 78 mounted on the rod 70. Nuts 82 and84 mounted on the rod outside of wheels 74 and 76 secure the wheels andthe member 78 in place on the rod 70.

In the embodiment of FIGS. 3 and 4 the centrifugal weights are guided ina radial'direction by positioning them with the wheels 74 and 76 oneither side of a flange 86 formed on the pulley flange 40. With thisarrangement, the bearing member 78 abuts flange 86 on the pulley flange40 and rolls therealong to reduce friction therebetween while theperiphery of the wheels 74 and 76 roll along the surface of cam ramp 62.The top half of FIG. 3 shows the clutch in a maximum speed mode whilethe bottom half shows the clutch in an idle mode.

With reference to FIGS. and 6, the centrifugal weight 66' shown thereinincludes a rod 87 having a single wheel 88 mounted thereon, a bearing 89mounting the wheel for free rotational movement on rod 84 and the rodfor rotational movement with respect to the wheel. The centrifugalweight 66' is mounted with the periphery of wheel 88 rolling on the camramp and the rod 87 rolling on a guide flange 90 mounted on the pulleyflange. A recess 92 is provided in the pulley flange to free theperiphery of the wheel from all contact except with the cam ramp. Thetop half of FIG. 5 shows the clutch in a high speed mode while thebottom half shows the clutch in an idle mode.

The embodiment of the centrifugal weight 66" shown in FIGS. 7-9 isalmost identical with that of FIGS. 3 and 4 and like numbers are used toindicate like parts. The difference between the two embodiments is theaddition in the embodiment of spaced guideways 94 on the cam ramp toprovide additional radial guidance to the centrifugal weight.

In operation, as the operator of the vehicle depresses the motorthrottle control to initiate movement of the vehicle, the motor RPMsincreases thereby increasing the angular velocity of the drive shaft.This causes the centrifugal weights 66, 66 or 66" to roll radiallyoutwardly, forcing the pulley flange 40 toward pulley flange 38 againstthe bias of spring 43. Initially, this causes the V-belt to be engagedby both pulley flanges and to be driven thereby. With continuedincreasing motor speed and drive shaft angular velocity, the centrifugalweights continue to roll radially outwardly and the cam rampprogressively forces pulley flange 40 toward pulley flange 38 and theV-belt 44 moves radially outwardly in groove 42. This exerts a radiallyinward pull on the V-belt portion between pulley flanges 48 and 50 andthe pulley flange 48 is displaced against the spring means in housing 58to accommodate the inward movement of the V-belt.

In this way, as the operator of the snowmobile increases his throttlepressure, the vehicle will go from a stationary idle to a high torque,low speed acceleration to a high speed, low torque cruise speed. Thebearingly mounted idler-type centrifugal weights enable changes invehicle speed to be made smoothly and with precision.

Having now fully set forth both structure and operation of preferredembodiments of the concept underlying the present invention, it may bethat various other embodiments as well as certain variations andmodifications of the embodiments herein shown and described will occurto those skilled in the art upon becoming familiar with said underlyingconcept. All such embodiments, variations, and modifications asincorporate the spirit of the invention and depend upon its underlyingconcept are consequently to be considered as within the scope of theclaims appended herebelow, unless the claims by their language expresslystate otherwise.

I claim:

1. In a centrifugal clutch including a drive shaft, a pair of pulleyflanges mounted on said drive shaft and providing therebetween a groovefor a V-belt, one of the pulley flanges being axially movable on thedrive shaft to vary the radial position of the V-belt with respect tothe pulley flanges, apparatus for axially moving said movable pulleyflange in response to the angular velocity of the drive shaft,comprising:

a cam ramp fixedly mounted to said drive shaft in spaced relationshipwith the side of the movable pulley flange away from the other pulleyflange,

said cam ramp including a portion curved toward said movable pulleyflange, and

a weight mounted for rolling radial movement on said movable pulleyflange and on said cam ramp, and

wherein said roller weight includes:

arod,

a pair of wheels mounted on said rod for rolling engagement with saidcam ramp, and

a bearing of smaller diameter than the wheels is mounted on said rodbetween said wheels for rolling engagement with said pulley flange, and

wherein said pulley flange includes a guideway extending toward the camramp radially outwardly therealong, and

said wheels are mounted on the rod in positions spaced laterally awayfrom the sides of the guideway such that the wheels are guided thereby.

2. Apparatus according to claim 1, wherein a pair of guide members aremounted on the cam ramp, spaced apart a distance sufficient to receiveboth wheels therebetween.

3. Apparatus according to claim 2, wherein a plurality of guideways aremounted on said pulley flange equidistantly therearound, a rollingweight is mounted on each guideway and a pair of guide members aremounted on the cam ramp to receive both wheels of each rolling weighttherebetween.

4. In a centrifugal clutch including a drive shaft, a pair of pulleyflanges mounted on said drive shaft and providing therebetween a groovefor a V-belt, one of the pulley flanges being axially movable on thedrive shaft to vary the radial position of the V-belt with respect tothe pulley flanges, apparatus for axially moving said movable pulleyflange in response to the angular velocity of the drive shaft,comprising:

a cam ramp fixedly mounted to said drive shaft in spaced relationshipwith the side of the movable pulley flange away from the other pulleyflange,

said cam ramp including a portion curved toward said movable pulleyflange, and

a weight mounted for rolling radial movement on said movable pulleyflange and on said cam ramp,

and wherein said roller weight includes:

a rod,

a wheel bearingly mounted on said rod for rotation with respect theretoand rolling engagement with said cam ramp,

a guideway mounted on said pulley flange and extending therefrom towardssaid cam ramp, said guideway having a recess therein to accept a portionof said wheel therein, and

the rod of said roller weight being mounted for rolling engagement withsaid guideway on both sides of said recess.

1. In a centrifugal clutch including a drive shaft, a pair of pulley flanges mounted on said drive shaft and providing therebetween a groove for a V-belt, one of the pulley flanges being axially movable on the drive shaft to vary the radial position of the V-belt with respect to the pulley flanges, apparatus for axially moving said movable pulley flange in response to the angular velocity of the drive shaft, comprising: a cam ramp fixedly mounted to said drive shaft in spaced relationship with the side of the movable pulley flange away from the other pulley flange, said cam ramp including a portion curved toward said movable pulley flange, and a weight mounted for rolling radial movement on said movable pulley flange and on said cam ramp, and wherein said roller weight includes: a rod, a pair of wheels mounted on said rod for rolling engagement with said cam ramp, and a bearing of smaller diameter than the wheels is mounted on said rod between said wheels for rolling engagement with said pulley flange, and wherein said pulley flange includes a guideway extending toward the cam ramp radially outwardly therealong, and said wheels are mounted on the rod in positions spaced laterally away from the sides of the guideway such that the wheels are guided thereby.
 2. Apparatus according to claim 1, wherein a pair of guide members are mounted on the cam ramp, spaced apart a distance sufficient to receive both wheels therebetween.
 3. Apparatus according to claim 2, wherein a plurality of guideways are mounted on said pulley flange equidistantly therearound, a rolling weight is mounted on each guideway and a pair of guide members are mounted on the cam ramp to receive both wheels of each rolling weight therebetween.
 4. In a centrifugal clutch including a drive shaft, a pair of pulley flanges mounted on said drive shaft and providing therebetween a groove for a V-belt, one of the pulley flanges being axially movable on the drive shaft to vary the radial position of the V-belt with respect to the pulley flanges, apparatus for axially moving said movable pulley flange in response to the angular velocity of the drive shaft, comprising: a cam ramp fixedly mounted to said drive shaft in spaced relationship with the side of the movable pulley flange away from the other pulley flange, said cam ramp including a portion curved toward said movable pulley flange, and a weight mounted for rolling radial movement on said movable pulley flange and on said cam ramp, and wherein said roller weight includes: a rod, a wheel bearingly mounted on said rod for rotation with respect thereto and rolling engagement with said cam ramp, a guideway mounted on said pulley flange and extending therefrom towards said cam ramp, said guideway having a recess therein to accept a portion of said wheel therein, and the rod of said roller weight being mounted for rolling engagement with said guideway on both sides of said recess. 